Hi jonathanclark,
Well now, I think you should be awarded the "Most Interesting Question
of the Day Award" (actually three questions) and while on the surface
may seem simple enough, the answer is highly complex as it involves
the balance of nature (ecology) and the inter-dependence of life. You
can't just pull a tree from the forest and explain its physiology and
anatomy without also explaining the structure of soil and how it
regenerates and so forth and so on.
Briefly, trees don't have a digestive system as we do so they aren't
"pulling matter from the ground" and digesting it - their fine root
system, located near the surface, take in macro-nutrients from the
soil to feed the tree. The decomposition of fallen leaves, dead wood,
insects, etc, serve to replenish the soil with organic nutrients, and
rocks break down to produce the inorganic (mineral rich) particles of
soil. Therefore, this constant cycle of growth and breakdown inhibits
soil depletion, ensuring not only food for the forest, but stable
footing as well (trees are anchored by a massive root system).
For an overview, here is an excellent place to start:
MICHIGAN FORESTS FOREVER TEACHERS GUIDE:
Tree Physiology:
http://www.dsisd.k12.mi.us/mff/Environment/TreePhys.htm
1) The break-down on what percent of a typical tree's is what
minerial/molecule.
An Introduction to Wood Anatomy Characteristics Common To Softwoods &
Hardwoods:
"All wood is composed of cellulose, lignin, ash-forming minerals, and
extractives formed into a cellular structure. The characteristics and
amounts of these components and differences in cellular structures
result in significant variations. Some woods are heavier, some
lighter, some stiffer, some more flexible, some harder, some softer,
and some easier to work with than others. It is these differences that
make wood such a unique material.
It is beyond this publication to do more than mention the different
chemical compositions of wood. Because harsh chemicals are needed to
separate some of these components from others, wood scientists do not
know everything about the structures and functions of some of these
chemicals. In addition, the components themselves are somewhat altered
during the separation processes."
In general terms, the chemical composition of wood from trees found in
the United States, on an oven-dry basis, can be summarized as follows:
Cellulose: 40 to 50 percent
Hemicellulose: 20 to 35 percent
Lignin: 15 to 35 percent
Ash: less than 1 percent
Miscellaneous compounds usually 1-2 percent
http://www.ca.uky.edu/agc/pubs/for/for59/for59.htm
TABLE OF ESSENTIAL ELEMENTS FOR PLANT GROWTH:
http://fig.cox.miami.edu/~tkoop/spring00/BLNtransport.htm
2) Where does the matter for those minerals/molecules come from?
"Soils are mixtures of organic and inorganic material that serve as
the source for all macro and micro nutrients except for carbon,
hydrogen and oxygen which plants take in from air and water. Soil
particles in nature are a result of breaking down of rocks which
produces the inorganic components of soil. These particles vary from
coarse sand to tiny particles of clay. Plants extract minerals from
the inorganic components and use them to synthesize the organic
components. When organisms die, the decomposing organic matter becomes
humus."
"So, how do plants get the nutrients from soil? Ideally, minerals
dissolve in the layer of water surrounding soil particles then move
into the roots for distribution to all parts of the plant. The path is
through the plasma membranes of the root hairs, across the cells of
the root cortex, and into the xylem. From there transpiration pulls
them along with water up the xylem to all plant organs. Plants have to
expend considerable energy to get the ions into the roots against a
concentrated gradient. It's part of the investment in energy that
every plant has to make."
http://www.lcbsbonsai.org/Newsletter/BasicBotany/Part06_PlantNutrientsandGrowth.htm
3) Why doesn't the ground collapse around a tree as it continues to
pull matter from the ground and transport it into the air - or does
it?
Plant Nutrients and Growth:
"An interesting anecdote regarding early scientific thinking about
plant nutrition is illustrative of some important concepts. Aristotle
had put forth the idea that plants derived most of their sustenance
from soil. Around 400 years ago, a Dutch physician named van Helmont
conducted an experiment using a willow tree. He put a willow with a
given weight in a pot after weighing both tree and soil. He watered
the tree for 5 years, took it out of the pot, removed and dried the
soil, weighed both soil and tree and discovered that the tree had
gained around 165 pounds while the soil had only lost 1 ounce in
weight. He was able to demonstrate that there was nothing inherent in
the soil itself that made the difference in the trees mass and that it
must have come from some other source."
http://www.lcbsbonsai.org/Newsletter/BasicBotany/Part06_PlantNutrientsandGrowth.htm
Forest Ecology:
"A forest is a community of living organisms which rely on one another
for their existence. The forest ecosystem is the interaction of the
living organisms and their physical environment. In the plantation
forest community those interactions produce energy in the form of food
being passed on from one trophic level (feeding level of an organism)
to another along food chains. Linking of food chains results in food
webs."
http://www.insights.co.nz/magic_habitat_fe.asp#
Additional Link:
The Ecology of Urban Trees:
"The fact that most trees have evolved in forests where the soil is
naturally mulched with leaves, dead branches, downed trees, and other
woody debris is lost on many people. By and large, forest soils are
cool, moist, fertile, well-structured, aerated, and biologically
active. Such conditions favor root development and plant growth."
http://www.urban-forestry.com/citytrees/v37n5a22.asp
Thank you for the interesting question. If you have any questions,
please post a clarification request before rating my answer.
Thank you,
hummer
Google Search Terms Used
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